The long-term objective of the project is to provide a basic understanding of ovarian cellular gonadotropin receptor regulation which will eventually be applicable to the problem of fertility regulation. This application is concerned with three general issues which continue the long-term project objective and summarize/encompass the specific aims of this proposal: a) the role of certain growth factors in key ovarian cellular differentiation processes such as FSH-dependent LH receptor induction, b) whether gonadotropins and/or sex steroids might, in turn, modulate receptor populations for growth factors, and c) the use of serum-free culture conditions to study receptor regulation in intact cells. The specific aims of the project consist of the following experimental objectives: 1) to test homogenous prepatations of platelete-derived growth factor (PDGF) upon FSH-stimulated LH receptor induction and upon subsequent LH receptor-dependent cell functions in porcine and rat granulosa cell monolayers, 2) to examine the possibility that a non-PDGF component of platelet extracts might facilitate FSH-stimulated LH receptor induction and/or selected subsequent LH receptor dependent cell functions, 3) to characterize granulosa cell PDGF receptor binding and study PDGF receptor modulation by reproductive hormones in granulosa cell monolayers, 4) to characterize granulosa cell epidermal growth factor (EGF) receptor binding and study EGF receptor modulation by reproductive hormones in vivo and in vitro, and 5) to extend our study of the serum-free culture milieu and the performance of cultured granulosa cells by a) investigating the effects of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) upon growth factor/gonadotropin-stimulated steroidogenesis, and b) characterizing the responses in culture of granulosa cell sub-populations preferentially enriched or lacking in a particular membrane receptor.